1. Field of the Invention
This invention relates generally to high pressure pumps, and more particularly to an improved valve assembly for high pressure reciprocating pumps.
2. Brief Description of the Prior Art
High pressure fluid delivery systems with reciprocating pumps are used to create a high pressure water jet for cleaning, or water jetting. Hydraulic pressures in excess of 10,000 psi may be present in various sections of these pumps, subjecting their parts to significant stress. The valve members in such pumps often require frequent repair or replacement due to the high pressures involved and the damage caused by impurities in the fluid being pumped.
Various types of valve assemblies have been used in high pressure reciprocating pumps including: (1) valve assemblies utilizing seats that are press-fitted into the pump fluid end cylinder body; (2) valve assemblies utilizing seats which are seated and retained in the pump fluid end cylinder body by means of a locking and sealing taper on the seat, such as shown by Elliott in U.S. Pat. No. 3,474,808; (3) valve assemblies utilizing tubular seats with circumferential O-ring seals which are inserted in cylindrical bores in the cylinder body, such as shown by Pacht in U.S. Pat. No. 4,277,229; and (4) disc seat style valve assemblies that are retained and sealed in the pump fluid end by being clamped between the cylinder body and manifolds that conduct the suction and discharge fluid to the cylinder body.
Several types of clamped disc seat style valve assemblies currently being used in high pressure reciprocating pumps utilize a spring cage which is integral with the seat disc. A press-fitted seat insert is utilized in this style but it has the same disadvantages as a press-fitted seat in the cylinder body in that any high pressure fluid that may bypass the insert causes erosion damage to the insert bore in the seat disc. The press-fitted seat insert in this style also has the disadvantage of requiring special tools for its replacement in the valve assembly. Another type of clamped disc seat style valve assembly currently in use is one in which the seat disc is "sandwiched" to a flange on the spring cage that is of the same diameter as that of the seat disc. This valve assembly is more expensive to manufacture than the disclosed valve assembly due to its unnecessarily large spring cage flange. It also has the disadvantage of requiring an additional high pressure seal to seal the mating faces between the spring cage flange and the sandwiched seat disc.
Mulvey, U.S. Pat. No. 4,140,442 discloses a valve assembly wherein an apertured cup-shaped valve housing having a flanged lower rim is pressed fitted within a stepped wall of the valve seat member to form an integral valve assembly. When the valve assembly is positioned in the port, a pair of O-rings are positioned on top and beneath the valve assembly.
Yaindl, U.S. Pat. No. 4,239,463 discloses a valve assembly in which the spring cage is retained in a circular bore by means of a snap ring.
Pangburn, U.S. Pat. No. 3,277,837 discloses a valve assembly having a plurality of segmented wedges or levers which are fulcrumed against a cylindrical plug at the cylinder head openings.
The present invention is distinguished over the prior art in general, and the above patents in particular by a valve assembly having a reusable spring cage that snaps onto a disposable seat disc. The valve and spring can be replaced or reused when the valve disc is replaced. The snap-type attachment of the spring cage to the seat disc allows the valve assembly to be handled and installed and removed from the pump fluid end as a one-piece assembly. A small flange on the spring cage where it snap attaches to the seat disc allows the spring cage to be securely clamped to the seat disc by the cylinder body and manifold when the valve assembly is installed in the pump fluid end. A modified seat disc having identical top and bottom surfaces may be inverted and reused.